CurtPalme.com Home Theater Forum

[zGman]

""" BUT, they do give a better MTF and beam power distribution profile than
the stock yokes. The stock yokes give a very classic Gaussian power distribution curve across the scan line, while the K-D yokes make the power distribution curve look more like a square wave and the power band is narrower and sharper than what you get with the stock yokes. """"


Yes - the increase in focus is not the issue here - Marquee focus can be very tight.

The issue is the variation of intensity across the line width, AND - a stock marquee
blooms horribly as constrast is increased, and all resolution is lost.

This happens in video more often than you think - explosions, sunlit scenes,
oncoming car headlights, etc...

The KD yokes retain beam control even as C goes up to 80's or 90's....

You may say that is not practical - but consider what one of the main
strengths of CRT is - the ability to channel all the power into a small
area of the raster, which make it able to reproduce effects like blinding headlights
and scorching deserts or sparkling water scenes. or big explosions, etc...

G

[mp20748]

[cmjohnson]

Exactly. The K-D yokes give a beam that doesn't bloom nearly as much at high drive levels. It seems fairly obvious to me that this is due to their longer magnetic field being "stiffer" due to the larger area they have to control the electron beam. You can drive to higher
contrast levels and retain sharpness, or retain more bloom resistance at peak output levels.

Particularly at higher contrast levels, this does contribute to an increase in EFFECTIVE resolution capacity, as frankly most of like a good
bright picture and are likely to run contrast levels above 50.

In my case I run contrast at around 70 BUT it's fair to note that the APL coming out of my Blu-Ray player into a Moome DVI input card
(via an adapter cable) seems to be a bit on the low side. Comparing it to the RGB inputs, the RGB inputs are brighter and I run lower
contrast settings (about 50 to 55) on those inputs.

With stock yokes you can watch the scan lines disappear when you crank up the contrast. With the K-D yokes, at least when they are
optimized or nearly so, the scan lines don't disappear with increasing contrast until the contrast value is getting silly.


CJ

[Mark_A_W]

[cmjohnson]

Actually, upon further investigation it is evident that you can use EITHER the 4-pole or 6-pole astig windings in a Marquee as both are wired with two phases. Whichever one works better is the one to use.

No thanks to the G90. No longer made, no longer supported, and with that so-far insurmountable issue with IC421, if someone gave me
a G90 I'd keep my Marquee so I can keep watching movies after the G90 smokes IC421 and becomes suitable only for keeping other
G90s alive....or donating its magnetics to a projector you'll still be able to get parts for 10 years from now.

The parts supply issues with G90s make them a poison pill today.


CJ

[zGman]

Oh gee whiz CJ - lets keep your propensity for hyperbole in check and stick with the fun technical discussions,
in which you do have good ideas and observations to share ----

There are plenty of reliable g90's out there and lots of satisfied owners...when properly setup
the g90 produces a stunning picture with unprecedented "pop" and incredible sharpness.

Yes there have been weird and frustrating problems, but the same is true for 909's and many others.

Yes the Marquee is a reliable chassis and there are lots of spares available, but new
parts are not cheep, and this whole discussion centers on the deficiencies of the stock
focus coils...!

Personally I am headed toward a SonMarBarQuee...with sony coils, marquee electronics,
Barco housings, and a 909 chassis to fit in my ceiling recess....hohoho!!!!

Cheers,
G

[stefuel]

[cmjohnson]

Using the G90 focus yokes (after properly modified for Marquee usage) with their 6-pole astig correction coils hooked up instead of the 4-pole coils should be exactly the cure for your triangular corner dots.


My inclination to not seek out a G90 due to parts availability issues with IC421 is strictly my own decision. I don't want to sink money
into a projector that can't be repaired if that part smokes, and it's a known issue with TOO many of them. You are of course welcome
to make a different cost/risk assessment if you wish to.

For me, the ideal projector would be a Marquee that outperforms a Cine 9 and a G90. Or at least equals them in every respect.

I'm starting to think that it's VERY possible to achieve that goal. The Marquee has the best video chain, and the rest is tubes,
magnetics, and optics. Optics are easy. HD-10Fs or HFQ900s CAN be found. Magnetics can be adapted and retrofit. Tubes are easy if you just spend the money.

Between those and the large variety of electronic tweaks, mods, and outright redesigns of various Marquee circuits, I think that there
is no major obstacle to getting that level of performance. But is it worth it? Again, that comes down to an individual cost/benefit
value judgement.

For me, I'm by far the most familiar with the Marquee chassis and obviously there's no shortage of parts and support for them, so
definitely I'm going to say that I think it's worth it to me. The only question is whether or not I actually can commit the time,
labor, and money to doing THAT much work on the projector.

I have my limits in terms of what I can afford to spend and how much time I can invest in it. I have too many hobbies and projects right now as it is. I have guitars to finish building, violins to repair, multiple electronic projects to work on BESIDES Marquee upgrades, and a huge work project that's giving me overtime, which is great for the wallet but bad for the amount of free time I have to work on other things.


CJ

[Sparky015]

[cmjohnson]

HD10Fs are reportedly the same thing as HFQ900s.

Several years ago I scored a brand new set of HFQ900s at a government surplus auction.

I tried them out but didn't see that they were any better than my GT17s so I sold them for a good profit, but in retrospect,
I sold them too cheap.

But, when I tried them out I wasn't running HD. I think I was at 800x600 at the time, which isn't high enough resolution
for the differences in lens types to be all that evident.

I might have observed more of a difference if I'd had 1080p available to me at the time.


I have HD10Fs now, and will be installing them as part of my refurb/upgrade on my machine that I'll be starting within the next
two weeks, with any luck.

CJ

[Sparky015]

Good luck with the project. Mine has been undergoing upgrades for over a year! I should be wrapping it up hopefully tomorrow though. The only thing missing are 10F or HDQ900 lenses. Maybe someday!

Interesting you didn't notice a difference between HFQ900 and GT17s. Could be that it's due to the tubes. If you don't have lugs or tubes that can do 10 lines rather than the stock 12, having lenses that can produce 10 is useless.

I look forward to hearing about your results when you get it wrapped up!

[cmjohnson]

I was running pretty low resolution at the time. The difference would have been more noticeable if I'd tried it out at higher resolutions, I think. At the time I hadn't yet done any focus enhancements on my machine, either. Stock yokes, etc.


A slight correction there: Resolution of 12 line pairs per millimeter is HIGHER resolution than 10 line pairs per millimeter.

I think that the significant differences between GT17s and HFQ900s is all in the corner focus quality. The central focus should be the same.


I'm looking forward to getting the results of my upgrade program, too! I've been accumulating the bits and pieces required for quite
some time and it's going to be an adventure getting it all done in a fairly short period of time.


There's other documentation that I'm gathering as well, on such things as quieting down the noise levels on all the power supply rails,
and I have some ideas about that. I'm thinking the thing to do is quiet them down close to the source, by installing filter modules
in the LVPS cable harness rather than doing all the mods to various boards. With a little creativity, I could install the new filter module
in some available space around the fan tray or maybe use that space between the HVPS and LVPS, so long as I don't do horrible
things to the necessary airflow. Modding the PS rails on all the boards would take days. Installing a filter assembly in the LVPS
harness could be done in a few hours once the whole unit is torn down.

I'm seriously considering enlisting the help of an engineer friend of mine who would certainly be able to help me design some effective
filtering for all those rails and help me get it built. I'd have to pay him for his time but it may be worth it.


CJ

[stefuel]

[macgyver655]

[stefuel]

[macgyver655]

[cmjohnson]

You're kind of missing the point, Chip.

It's not about getting a digital-like image. It's about optimizing the system to the point that it CAN get too sharp, and then you soften
it up until it's just like perfectly focused film.

As time goes on and components age and drift, there will inevitably be some degradation in the resolution capability of any given projector,
so giving it surplus capacity allows you to readjust later down the road (between overhauls) and get back to an optimal picture.

If the very best that a perfect brand new projector can do is resolve 1080p fully, in five years it's going to be a bit soft and there won't
be anything you can do about it short of overhaul it and replace drifted components.

If that same projector can easily resolve 1080p AND even higher resolutions, then in five years it'll still be able to fully resolve 1080p
without having to do anything to it.

It's about greater reserve capacity.


It's also about the challenge of improving something. That's a hobby in and of itself.

CJ

[macgyver655]

If you ask me its all about kickin back with a beer in one hand and the remote in the other and just watching the damn thing.
I dont know how you anal retentive guys can even enjoy a movie. If I'm more worried about the little, itsie bitsie things that you have to try and find that dont look right, how do you even watch crap. Half of this sh*t you guys are chasing are only visible on test patterns. And if thats all you watch........... I just shake my head........

[Sparky015]

I'm just trying to get my machine to fully resolve 1080p, period. In order to do that, some upgrades are necessary. You can't magically turn a CRT into a digital. It's not going to happen. Two different technologies. I just want my CRT to do 1080p, and do it well, just like a G90 or 909. If I had the cash to start with, I would have bought one of those. Since I don't, and I want to be able to service the thing for years to come until I can afford the next technology, Marquee it is.

Sounds like you guys aren't enjoying the holiday. Put back a few more!

[km987654]